There was an unbilled addition to the Olympian collection of rock legends gathered at Indio, Calif.’s Desert Trip festival in October: Lars Ulrich of Metallica. But the drummer wasn’t onstage, sitting in with Roger Waters or Nobel laureate Bob Dylan — he was rocking out as a fan.

“Saturday, for Neil Young and Paul McCartney, I was actually in the pit,” Ulrich reports 14 days later. “Neil Young was going off.” Ulrich and his wife started 20 rows back but kept moving forward, like enthusiastic teenagers at their first rock show. By the end of the set, they were five rows back, about 25 feet from the stage. Ulrich jokes that he was waving at Young and calling out to him: “Hey, Neil! I’m playing with you in two weeks! I’ll see you at Shoreline!”

Today, sitting in a locker-room-like office of the Shoreline Amphitheatre in Mountain View, Calif., Ulrich yawns. He just woke up from a nap — he fell asleep while being driven to the venue for Neil Young’s annual all-star acoustic concert benefitting the Bridge School — and was briefly uncertain whether he was in the United States or Ecuador. (Metallica is scheduled to play Quito, Ecuador’s capital, at the end of the month.) “That shouldn’t be the primary theme of the story,” he says with a bleary smile.

Metallica, founded by Ulrich and singer-guitarist James Hetfield in 1981, got started a bit later than the Desert Trippers, but since Nielsen Music began tracking sales in 1991, it has sold more than 56 million albums, a number exceeded by only Garth Brooks and The Beatles. Metallica’s self-titled 1991 disc, known as The Black Album, has moved well over 16 million copies alone, making it the best-selling record of the era.

On Nov. 18, the band releases its 10th album, Hardwired... To Self Destruct, and while the band members’ finances remain secure, their role in musical culture is less clear. Whereas the Desert Trip acts can claim the mythic land of the ’60s, Metallica has persevered in a more nebulous territory, mapped out by high volume, bleak lyrics and bloody-knuckled riffs. “We know we’re not supposed to mature in this field. People don’t want you to,” says Hetfield later that day, in a separate (and slightly fancier) office at the venue. “They want you to look young and cool and dye your hair and all that shit. We respect our age — we’re not trying to hide it.” Up close, Hetfield is as intense as the guy howling his way through dozens of Metallica videos — but also friendly and quick-witted. “I’m pretty vulnerable most of the time,” he admits.

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Hetfield’s goatee is all salt, no pepper; underneath his baseball cap, Ulrich’s hairline has receded to the dark side of the moon. But when it comes to the inevitable process of aging, the question for Metallica isn’t vanity, but how long the band can keep making its physically punishing music — Hetfield and guitarist Kirk Hammett are 53, while Ulrich and bassist Robert Trujillo are 52. “Whether we’ll be able to play ‘Master of Puppets’ in our 70s, I just don’t know,” says Ulrich, referring to the group’s landmark 1986 thrash-metal anthem. “With Metallica, there’s a physicality and a weight that has to be part of it. You can play it less heavy, slower — or you can realize that the music deserves that physical approach, and if the physical delivery isn’t there, then maybe it’s better not to do it.”

Hetfield figures his body will tell him when it’s time to stop. While the band was dissolute enough in its early years to be nicknamed “Alcoholica,” Hetfield is sober, and the guys all get enough sleep and travel with a staff dedicated to keeping them in good physical shape. “You’re trying to prevent something from going off the rails,” says Ulrich. “We’re lowering the percentages of anything” — parts of their bodies, that is — “breaking midshow.”

Most of Metallica’s hard-rock peers from the ’80s and ’90s have faded away, or crashed and burned. Guns N’ Roses could have given it a run for the title of the defining rock act of Generation X, had it not been crushed under the weight of Axl Rose’s ego. But although Metallica has had to weather death (of original bassist Cliff Burton, in 1986), addiction and vicious infighting, the band members’ instincts during every crisis have been to keep making music, no matter what: radical, uncompromising music that sells millions of albums. “Their music was an amazing blend of aggression and virtuosity I didn’t find in other places” as a kid, says Mike Einziger, guitarist for the band Incubus (and co-author of Avicii’s hit “Wake Me Up!”), which has opened up for the group many times. “Metallica made it really cool to sell out stadiums all over the world.”

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The band hasn’t gone on the road full-time since its 2008-10 World Magnetic Tour, but it has a steady diet of big shows. In 2014, the group grossed $24.84 million on just eight of its dates, and the band took home more than $5 million when it played Minneapolis in August, according to Billboard Boxscore.

So who are Metallica’s role models for working past retirement age? “Everybody mentions The Rolling Stones,” says Hetfield. “They could probably play until they’re 120. Lemmy [of Motorhead] gave it all he had to the last breath. Bruce Springsteen, another guy I admire for his endurance. But Angus Young [of AC/DC] — that guy blows my mind. That guy sweats so much every night. I can’t believe his head is still on his body.”

Ulrich has a more drummer-oriented perspective: Of the six acts at Desert Trip, he notes, “the bad news is that the only O.G. drummer in the house was in The Rolling Stones. The only road map is Charlie Watts. I can see doing it in my 70s, mentally, but I just don’t know about the physicality. That remains the great question mark.”

In 2012, Metallica’s master recordings all reverted to the band from Warner Music Group, and the group now sells them through its own Blackened Recordings (handled by Metallica’s longtime manager, Cliff Burnstein). Hardwired... To Self Destruct is the first new album the band is releasing on Blackened. The first step in making it was clearing the members’ schedules. “You plan years in advance,” says Burnstein. “You want to hold multiple nights at a venue somewhere? Stake your claim a year-and-a-half before you want to play there.” The band then hired producer Greg Fidelman, who engineered 2008’s Death Magnetic (produced by Rick Rubin) and co-produced 2011’s Lulu (the group’s oil-and-water collaboration with Lou Reed). The band set up shop at its HQ, a building owned by Metallica in tony Marin County, just north of San Francisco, and started recording in early 2015.

Rather than methodically building a dozen songs up, the group would work on three or so tracks, take a break to play a festival or attend to the deluxe Blackened reissue of an early album like 1984’s Ride the Lightning, and then come back to work on a few more songs. Having immersed themselves so deep and for such long stretches when making records like The Black Album, they wanted to ensure they would have better life balance. Fidelman says their aversion to long stretches in the studio stems from something “like PTSD.”

Metallica generally worked from 10 a.m. to 6 p.m. in its rehearsal space that the group calls “the jam room.” The quartet set up in a circle, with everyone facing Ulrich. The band members didn’t arrive with much in the way of finished songs, but what they did have were more than 1,000 riffs that they had cooked up in “the tuning room,” where they play together backstage before starting a live show. On tour, the tuning room might be the first place the members see each other all day.

“The tuning room is pretty much our couch therapy session,” says Hetfield. “You can tell where everyone’s at. Sometimes we’ll goof around — I love playing drums, and I’ll hit the kit while Rob comes up with some funky thing that we’ll never use.” One tradition, insisted upon by Ulrich: They always finish up by playing the song that will start the show. “Lars is ritualistic to a fault,” says Hetfield, “but he knows what works for him.”

The dynamic in Metallica was at one point dysfunctional enough that the band made a movie, 2004’s Some Kind of Monster, about its power struggles and its employment of a group therapist. “We’re more forgiving to differences of opinion now,” says Ulrich. “Twenty years ago, we’d go in there and battle for everything, whether it was creative ideas or personal preferences or whatever. Now, it’s just not worth it. We prioritize getting along and having a functioning entity — that’s more important than winning an argument.”

“We know so much about each other and we know which buttons not to push,” adds Hetfield. “I don’t have to be like Lars, and he doesn’t have to be like me. We try not to step on each other’s toes but guide each other. He’s great at set lists and arranging songs and business. I’m good at melodies and visuals and logos.” And the members outside the core duo? “Kirk, now that he has stepped out of his referee role, brings a wackiness that is very needed, because Lars and I can get so wound and serious. And live, obviously his guitar playing is unbelievable,” says Hetfield. “And Rob is so happy to be alive, it makes us want to do things so he’ll come along.”

Hardwired... to Self Destruct has a dozen songs, split between two CDs (for reasons of pacing — it could have fit on one). “Spit Out the Bone” is a relentless seven-minute fusillade inspired by the dangers of virtual-reality technology. “Dream No More” is a grinding nightmare that reaches back to the mythology of H.P. Lovecraft. The moral of “Now That We’re Dead” is that love endures, but only in the grave. You can guess the answer to the title of “Am I Savage?” The overall impact is bleak — the band even rejected a triumphant song that had become a live staple, “Lords of Summer,” because it didn’t fit the mood. Asked if he’s in a good place personally, Hetfield says, “Definitely not.” Then he laughs. “I’m in both places all the time, you know? But once I start thinking, it can get dark. The last song we wrote, ‘Hardwired,’ which is the opening track and the fastest one, sums it up lyrically: We’ve always been f—ed, but we survive. Every generation says ‘I feel sorry for the next generation,’ but there is a faith that you have in mankind. Most of the time.”

He grins. “I overthink everything.”

Music has long helped Hetfield get out of his own head — onstage, he can achieve a state of grace where he isn’t thinking. To reach that blissful place, he also used to skateboard, which turned into an eight-year obsession with snowboarding until he ruined his knees. Now he loves rafting, biking and stand-up paddleboarding. He recently agreed to relocate his family to Colorado for a year — he and wife Francesca, who first lived in the state after coming to the United States from Argentina, have three teenagers — on the condition that they drive there. They rented a CruiseAmerica RV and road-tripped through Yosemite, re-creating Hetfield’s childhood vacations. “It seemed like the right time to unplug the kids from this Marin bubble,” he explains, “and plug them into a different bubble.”

Hetfield praises Francesca, whom he met in 1992 when she toured with the band, working in the wardrobe department, and married in 1997: “She has been such a gift to this family. She drives a tight ship, if that’s even the right simile. If it even is a simile...” He trails off, looking for the right word. “Metaphor!”

A week before the Shoreline show, Hetfield went out hunting elk, and was terrified when high winds felt like they would either rip his tent apart or knock a tree branch on his head. “It’s nice to go out in the wilderness and get scared once in a while,” he says. “You get right-sized again.” He says that the appeal of hunting is knowing where his dinner came from. “I love being part of the process. My kids, they definitely don’t want to be part of the process.” Plus, he’s fundamentally attracted to guns: “I’ve always loved loud, fast things. Whether it’s bikes, cars or music. I’ve gotten into the long-range shooting now — I like that kind of challenge.”

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Ulrich — who also lives in Marin County, is married to the model Jessica Miller and has two teenage boys from an earlier marriage, as well as a younger son with the Danish actress Connie Nielsen — cultivates less visceral interests: Aside from his fondness for rock festivals, he loves books and films. “I do normal things — we carved pumpkins the other day with my kids,” he says. While he was once the band’s point man in its crusade against the file-sharing service Napster, today he’s unstressed by streaming. “It’s not something I sweat over,” he says. “I have the Spotify app and I use it, not daily but weekly. I’m on iTunes every day, more for movies than music. I’m on YouTube 500 times a day. We just won’t give these guys an exclusive — we don’t need the money, and we’d like all our fans to be able to find us.”

Metallica has had five No. 1 Billboard 200 albums in a row dating back to 1991, but the band knows that rock commands a much smaller slice of the music world now. Ulrich acknowledges that hip-hop is dominant, and makes a point of saying that he finds artists like Kendrick Lamar and Drake to be “inspiring and awesome.” But he also notes that “there are lots of 14-year-old kids in Latin America that still love rock music.” In the 21st century, Metallica is a global enterprise. The bottom line? “We’ve been parked just left of the mainstream for the better part of 30 years. We take care of ourselves, and we have a lot of elbow room.”

A few hours after the interviews, Metallica takes the stage for a crowd that has already seen acoustic performances from Willie Nelson, Roger Waters and host Neil Young. They deliver an unplugged set that’s heavy on covers, including Deep Purple’s “When a Blind Man Cries,” The Clash’s “Clampdown” and a rocket-fueled version of Buffalo Springfield’s “Mr. Soul” where the group is joined by Young. Through the years, Metallica has proved that its appeal transcends the California speed-metal scene, fans of complex time signatures and, indeed, the English language. It turns out that the group doesn’t even need high volume: Playing acoustic, Metallica is still full of authority and menace.

Hetfield can sound like the herald of the apocalypse, but tonight, he’s loose and funny. He tells the crowd, “There are some amazing artists up here playing — and then there’s us.” When Metallica attempts its new single “Hardwired,” he warns, “It’s kind of too fast for acoustic — but we don’t care, really.” The group bollix it up and has to restart, and as soon as it’s over, the band members are trading jokes about how Metallica won’t make it to its 36th year. They’re the sort of jokes you can make when your position in the rock firmament is secure. When Metallica started, its music was shockingly avant-garde. If it sounds less so as the decades go by, that’s not because the members have compromised themselves, but because they’ve changed the boundaries of popular music.

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Ulrich has a metaphor he likes (unless it’s actually a simile). Some guys his age build a “man cave,” a room where they can hang out with their buddies and watch football. He has a happy domestic life with his family, but Metallica is his man cave. “We run off with a rock n’ roll band,” he says. “That’s the fun part of my life.”